Electrophysiology is the study of electrical impulses through the heart and is focused primarily on diagnosing and treating arrhythmias, conditions in which electrical impulses within the heart vary from the normal rate or rhythm of a heartbeat. The most common arrhythmia is atrial fibrillation (AF), which is characterized by rapid, disorganized contractions of the heart's upper chambers, the atria. AF results from abnormal electrical impulses propagating through aberrant myocardial tissue pathways, which leads to ineffective pumping of the blood through the heart, as well as other complications. Atria flutter (AFL), another type of arrhythmia, is characterized by a rapid beating of the atria. Unlike AF, AFL arises from a single electrical wave that circulates rapidly throughout the right side of the heart. Since this arrhythmia can arise from multiple electrical sites, effective treatment requires electrical isolation of the aberrant signal sites, thereby forcing the heart's normal conduction pathway to take over.
The practice of interventional electrophysiology for treating arrhythmias, such as AF and AFL, generally involves inserting specialized catheters into a patient's vasculature and navigating the distal (or “working”) end of the catheters into the patient's heart chambers to identify (or “map”) the locations of heart tissue that are a source of the arrhythmias. The mapping of the heart's electrical activity is typically accomplished using one or more pairs of electrodes, each pair spaced apart axially along the working end of the catheter. Following or in conjunction with the mapping procedure, the attending physician may use an ablation catheter to disable (or “ablate”) the tissue containing the aberrant signal(s) or signal pathway(s), thereby restoring the heart to its normal rhythm.
While catheters may be provided with combined mapping and ablation functionalities, separate mapping and ablation catheters are more typically used, which allows for much greater capability of their respective functions. For example, electrical activity is normally mapped using much smaller electrodes (in surface area) than are used for performing ablation procedures. Because there is significantly less current transmitted through a mapping electrode circuit than through an ablation circuit, the lead wires that connect the mapping electrodes to processing circuitry (e.g., via a pin connector in the catheter handle) are much smaller than are used to couple ablation electrodes to an RF generator. As such, a much greater number of electrodes may be provided on a mapping catheter than on an ablation catheter having a same or similar profile.
For AFL mapping procedures (as well as for some AF procedures), it is important to map the electrical activity in both the coronary sinus (CS) and the right atrium (RA), especially the region of the high right atrium (HRA). Currently, to map both the CS and the RA, a pre-shaped, non-steerable, mapping catheter having two sets of electrodes is inserted through a jugular vein at the base of the patient's neck, through the superior vena cava (SVC), and into the RA, where it bends (or “banks”) off of the lower portion of the atrial chamber (i.e., over the isthmus region) and into the CS. While functional for mapping the respective RA and CS, this type of catheter has certain drawbacks. For example, because it passes across the lower atrial chamber, maneuvering the mapping catheter for achieving proper electrical contact in the HRA can be difficult. Further, since most ablation catheters used for AFL and AF interventional procedures are inserted through the groin and inferior vena cava (IVC), and are maneuvered to ablate tissue in the isthmus region of the lower atrial chamber, the mapping catheter extending across the isthmus can block and interfere with the ablation catheter. Plus, the patient and attending physician must cope with having two different access ports into the patient's venous system (i.e., both through the jugular and through the groin), making simultaneous control of the respective mapping and ablation catheters more difficult, and increasing the chances of related complications and patient discomfort.
While there are diagnostic catheters available for mapping the RA and HRA through groin access and the IVC, these typically form a complete distal end loop that encircles the atrial chamber, with a small tail segment for slight penetration into the ostium of the CS. The loop portion extends over the isthmus region in the lower right atrium (LRA), interfering with the ablation catheter, and the limited penetration of the CS results in corresponding limited CS mapping data.
Thus, it would be desirable to provide a diagnostic catheter that may be better positioned for mapping both the HRA and the CS, which is inserted through the groin and IVC, without blocking the isthmus.